This invention relates to systems and implants for ligament reconstruction or bone reconstruction.
Reconstructions of the cruciate ligaments are among the most frequently performed procedures in knee surgery nowadays. The most common method for re-constructing a torn cruciate ligament involves a bone-patellar tendon graft or a semitendinous graft, which is frequently fixed with metal (e.g. titanium or stainless steel) interference screws. The metal interference screws offer the advantage of a permanent implant with adequate mechanical strength. Sharp threads of the metallic interference screws may harm the transplant. In addition, years after the cruciate ligament reconstruction a revision is difficult to realize due to a bony sheating of the metal implants and often is associated with iatrogen damage.
Alternatively, resorbable interference screws made from PLLA, PDLLA, PLLA/TCP (e.g. 70%/30%) have been used with specially designed threads in order not to cut the tendon transplant. However, drawbacks such as loosening fixation, bone resorption and inflammatory reactions have been reported in literature.
In a different common method, the semitendinous tendon is used as a transplant for the reconstruction of the cruciate ligaments. It is often attached with an inter-connection cord using a fixation distant to the articular. Due to the length and the polynominality of the reconstruction, the fixation may result in deterioration of stiffness and micro movements in the bone channel. Proximal articular fixation systems for semitendinous plasty are performed by inserting a transcondylar pin made of metal or PLLA. Beside the drawbacks of the used materials tunnel enlargement of the drilling tunnel (tunnel enlargement) can be observed in some cases.
The present invention also relates to systems and implants for bone reconstruction which may be necessary if a vital bone structure has collapsed due to too high loads. According to the prior art, a collapsed joint is reconstructed by drilling a bore from a side of the bone which is opposite to the collapsed surface. The collapsed surface is then reduced into the correct anatomical position by introducing a pestle into the bore and by pushing this pestle against the collapsed surface. After the original shape of the collapsed surface has been reestablished, the remaining void under the reshaped surface is filled by a bone replacement material. An example for such a bone replacement material is a cement material as for example described in U.S. Pat. No. 6,733,582 B1. The advantage of this material is that it is biodegradable and is replaced by vital bone structure over the time. However, the replacement material is restricted to applications with minor loadings, because it has a high porosity and contains macro holes in the size of 100 to 500 micrometers which are necessary in order to achieve a fast ingrowth of the vital bone structure.